Multiplexing detector constructed from fabric

ABSTRACT

A position detector is constructed from fabric and has electrically conductive elements. The detector is configured to produce electrical outputs in response to mechanical interactions, and is divided into several regions. Each of the regions includes a first conducting plane and a second conducting plane configured such that, in use, a mechanical interaction results in conducting planes of at least one of said regions being brought closer together. A potential is applied across at least one of said planes to determine the position of said mechanical interaction.

FIELD OF THE INVENTION

[0001] The present invention relates to a detector constructed fromfabric having electrically conductive elements to define at least twoelectrically conductive planes.

INTRODUCTION TO THE INVENTION

[0002] A fabric touch sensor for providing positional information isdescribed in U.S. Pat. No. 4,659,873 of Gibson. The sensor is fabricatedusing at least one resistive fabric layer in the form of conductingthreads. This fabric is constructed using either unidirectional threadsor crossed threads formed by overlaying one set with another or weavingthe two sets together. The fabric is separated from a second resistivelayer to prevent unintentional contact by separators in the form ofnon-conducting threads, insulator dots or with an air gap. Bothresistive layers are fabrics formed from conductive threads such that nopre-forming is required in order to adapt the sensor to a contouredobject.

[0003] A problem with the sensor described in the aforesaid UnitedStates patent is that it is only capable of identifying the location ofthe mechanical interaction and cannot provide additional informationabout the interaction.

[0004] A touch sensor for providing positional information is describedin U.S. Pat. No. 4,487,885 of Talmage, which also provides a signaldependent upon the pressure or force applied. However, the sensordescribed is made from a printed circuit board and a flexible sheet ofrubber, elastomer or plastic and as such it does not have the manyphysical qualities that a fabric may provide.

SUMMARY OF THE INVENTION

[0005] According to a first aspect of the present invention, there isprovided a position detector constructed from fabric having electricallyconductive elements, comprising at least two electrically conductingplanes, wherein an electric potential is applied across at least one ofsaid planes to determine the position of a mechanical interaction; and asecond electrical property is determined to identify additionalproperties of said mechanical interaction.

[0006] In a preferred embodiment, the position detector is configured tomeasure current or resistance as said second electrical property.Furthermore, applied force, applied pressure, area of contact ororientation of an object may be determined as the additional property ofmechanical interactions.

[0007] In a preferred embodiment, the detector interacts mechanicallywith parts of a human body; a first electrical property determines theposition of a mechanical interaction and a second electrical propertydetermines the area of coverage.

[0008] According to a second aspect of the present invention, there isprovided a method of detection, performed with respect to a detectorconstructed from fabric and having electrically conductive elementsconfigured to provide at least two electrically conducting planes,comprising the steps of applying a potential across at least one of saidplanes to determine the position of a mechanical interaction, andmeasuring a second electrical property to identify additional propertiesof said mechanical interactions.

[0009] According to a third aspect of the present invention, there isprovided a detector constructed from fabric having electricallyconductive elements and configured to produce electrical outputs inresponse to mechanical interactions, wherein said detector is dividedinto a plurality of regions; each of said regions includes a firstconducting plane and a second conducting plane; a mechanical interactionresults in conducting planes of at least one of said regions beingbrought closer together; and a potential is applied across at least oneof said planes to determine the position of said mechanical interaction.

[0010] According to a fourth aspect of the present invention, there isprovided a detector constructed from fabric having electricallyconductive elements to define at least two electrically conductingplanes and configured to produce an electrical output in response to amechanical interaction, wherein a potential is applied across at leastone of said planes to determine the position of a mechanical interactionand said second electrical property is determined to identify additionalproperties of said mechanical interactions; and a conductivitynon-uniformity is included in at least one of said planes so as tomodify an electrical response to a mechanical interaction.

[0011] In a preferred embodiment, the conductivity non-uniformityincludes a co-operating pair of conducting strips configured to generatea substantially linear electric field within the conducting planes.Preferably, the strips are applied to each of the conducting planes atorthogonal locations.

[0012] According to an alternative preferred embodiment, all edges ofthe conducting planes are modified. The conductivity non-uniformity maybe defined by adjusting the density of conducting threads or it may becreated by printing conductive materials onto the detector.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 shows a position detector constructed from fabric;

[0014]FIG. 2 shows a control circuit identified in FIG. 1;

[0015]FIG. 3 details operations performed by the micro-controlleridentified in FIG. 2;

[0016]FIG. 4 details planes identified in FIG. 1;

[0017]FIG. 5 details current flow due to mechanical interaction;

[0018]FIG. 6 details an alternative construction for conducting fabricplanes;

[0019]FIG. 7 shows an alternative configuration of conducting planes;

[0020]FIG. 8 shows an alternative configuration of conducting planes;

[0021]FIG. 9 details a composite configuration of conducting planes; and

[0022]FIG. 10 shows an asymmetric object interacting with conductingplanes.

[0023]FIG. 11A and FIG. 11B show an alternative construction for adetector;

[0024]FIG. 12A and FIG. 12B show a further alternative construction;

[0025]FIG. 13 shows a further alternative construction;

[0026]FIG. 14 shows a further alternative construction.

[0027]FIG. 15 shows an alternative embodiment having a plurality ofdetectors;

[0028]FIG. 16 shows an alternative detector configuration; and

[0029]FIG. 17 shows multiple detectors of the type shown in FIG. 16.

[0030]FIG. 18 shows a first embodiment in which a connector has beenincluded during the machining process; and

[0031]FIG. 19 shows an alternative embodiment in which a connector hasbeen added during a machining process.

[0032]FIG. 20 shows a detector constructed from fabric having aconductivity non-uniformity; and

[0033]FIG. 21 shows an alternative embodiment with a conductivitynon-uniformity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The invention will now be described by way of example only withreference to the previously identified drawings.

[0035] A position detector 101 constructed from fabric is shown inFIG. 1. The detector has two electrically conducting fabric planes, inthe form of a first plane 102 and a second plane 103. The planes areseparated from each other and thereby electrically insulated from eachother, by means of an insulating mesh 104. When force is applied to oneof the planes, the two conducting planes are brought together, throughthe mesh 104, thereby creating a position at which electrical currentmay conduct between planes 102 and 103. In this way, it is possible toidentify the occurrence and/or position of a mechanical interaction.

[0036] The fabric planes are defined by fabric structures, which may beconsidered as a woven, non-woven (felted) or knitted etc. The fabriclayers may be manufactured separately and then combined to form thedetector or the composite may be created as part of the mechanicalconstruction process.

[0037] When a voltage is applied across terminals 107 and 108, a voltagegradient appears over plane 102. When a mechanical interaction takesplace, plane 103 is brought into electrical contact with plane 102 andthe actual voltage applied to plane 103 will depend upon the position ofthe interaction. Similarly when a voltage is applied between connectors111 and 112, a voltage gradient will appear across plane 103 andmechanical interaction will result in a voltage being applied to plane102. Similarly, the actual voltage applied to plane 102 will depend uponthe actual position of the interaction. In this way, for a particularmechanical interaction, it is possible to identify locations within theplane with reference to the two aforesaid measurements. Thus, connectors107, 108, 111 and 112 are received by a control circuit 121, configuredto apply voltage potentials to the detector 101 and to make measurementsof electrical properties in response to mechanical interactions.

[0038] Control circuit 121 identifies electrical characteristics of thesensor 101 and in response to these calculations, data relating to thecharacteristics of the environment are supplied to a data processingsystem, such as a portable computer 131, via a conventional serialinterface 132.

[0039] Control circuit 121 is detailed in FIG. 2. The control circuitincludes a micro-controller 201 such as a Philips 80C51 running at aclock frequency of twenty megahertz. Operations performed bymicro-controller 201 are effected in response to internally storedcommands held by an internal two kilobyte read-only memory. Themicro-controller also includes one hundred and twenty-eight bytes ofrandomly accessible memory to facilitate intermediate storage whileperforming calculations. Micro-controller 201 includes a serialinterface 202 in addition to assignable pins and an interface forcommunicating with an analogue to digital converter 203, arranged toconvert input voltages into digital signals processable by themicro-controller 201.

[0040] The control circuit 121 includes two PNP transistors 211 and 212,in addition to four NPN transistors 213, 214, 215 and 216. All of thetransistors are of relatively general purpose construction and controlswitching operations within the control circuit so as to control theapplication of voltages to the position detector 101.

[0041] In operation, measurements are made while a voltage is appliedacross first plane 102 and then additional measurements are made while avoltage is applied across the second plane 103; and output voltage onlybeing applied to one of the planes at any particular time. When anoutput voltage is applied to one of the planes, plane 102 or plane 103,input signals are received from the co-operating plane 103 or 102respectively. Input signals are received by the analogue to digitalconverter 203 via a selection switch 221, implemented as a CMOS switch,in response to a control signal received from pin C6 of themicro-controller 201. Thus, in its orientation shown in FIG. 2, switch221 has been placed in a condition to receive an output from a firsthigh impedance buffer 222, buffering an input signal received from plane102. Similarly, when switch 221 is placed in its alternative condition,an input is received from a second high impedance buffer 223, configuredto receive an input signal from plane 103. By placing buffers 222 and223 on the input side of CMOS switch 221, the switch is isolated fromhigh voltage electrostatic discharges which may be generated in manyconditions where the detector undergoes mechanical interactions.

[0042] In the condition shown in FIG. 2, switch 221 is placed in itsupper condition, receiving input signals from buffer 222, with outputsignals being supplied to the second plane 103. Further operation willbe described with respect to this mode of operation and it should beappreciated that the roles of the transistor circuitry are reversed whenswitch 221 is placed in its alternative condition. As previously stated,condition selection is determined by an output signal from pin C6 ofmicro-controller 201. In its present condition the output from pin C6 islow and switch 221 is placed in its alternative configuration when theoutput from pin 6 is high.

[0043] Output pin C0 controls the conductivity of transistor 211 withpins C1 to C5 having similar conductivity control upon transistors 213,214, 212, 215 and 216 respectively.

[0044] Transistors 211 and 213 are switched on when a voltage is beingapplied to the first plane 102 and are switched off when a voltage isbeing applied to the second plane 103. Similarly, when a voltage isbeing applied to the second plane 103, transistors 212 and 215 areswitched on with transistors 211 and 213 being switched off. In theconfiguration shown in FIG. 2, with switch 221 receiving an input frombuffer 222, output transistors 211 and 213 are switched off with outputtransistors 212 and 215 being switched on. This is achieved by outputpin CO being placed in a high condition and pin Cl being placed in a lowcondition. Similarly, pin C3 is placed in a low condition and pin C4 isplaced in a high condition.

[0045] In the configuration shown, C3 is placed in a low condition, aspreviously described. The micro-controller 201 includes a pull-downtransistor arranged to sink current from the base of transistor 212,resulting in transistor 212 being switched on to saturation.Consequently, transistor 212 appears as having a very low resistance,thereby placing terminal 111 at the supply voltage of five volts.Resistor 231 (4K7) limits the flow of current out of themicro-controller 201, thereby preventing burn-out of themicro-controller's output transistor.

[0046] Pin C4 is placed in a high state, resulting in transistor 215being placed in a conducting condition. A serial resistor is notrequired given that the micro-controller 201 includes internal pull-upresistors, as distinct from a pull-up transistor, such that current flowis restricted. Thus, transistors 212 and 215 are both renderedconductive, resulting in terminal 111 being placed at the positivesupply rail voltage and terminal 112 being placed at ground voltage. Thecapacitors shown in the circuit, such as capacitor 219, limit the rateof transistor transitions thereby reducing rf transmissions from thesensor 101.

[0047] With transistors 212 and 215 placed in their conductivecondition, input signals are received from the first plane 102 in theform of a voltage applied to terminal 108. For position detection, thisvoltage is measured directly and transistor 214 is placed in anon-conductive condition by output pin C2 being placed in a lowcondition. Under these conditions, the voltage from input terminal 108is applied to analogue to digital converter 203 via buffer 222 andswitch 221.

[0048] In accordance with the present invention, a second electricalproperty is determined which, in this embodiment, represents the currentflowing through the sensor in response to a mechanical interaction. Thecurrent measurement is made by placing transistor 214 in a conductivecondition, by placing output pin C2 in a high condition. In thiscondition, current received at terminal 108 is supplied to transistor214 via resistor 214A, having a resistance of typically 5 k selectableso as to correspond to the characteristics of the sensor. A voltage issupplied to A to D converter 203 via buffer 222 and switch 221 but onthis occasion the voltage represents a voltage drop, and hence acurrent, across resistor 214A.

[0049] Thus, transistors 212 and 215 are placed in a conductingcondition, transistor 214 is placed in a non-conducting condition, so asto measure voltage, and is then placed in a conducting condition so asto measure current. The roles of the transistors are then reversed, suchthat output transistors 211 and 213 are placed in a conductingcondition, with transistors 212 and 215 being placed in a non-conductingcondition (and switch 221 reversed) allowing a voltage to be measured byplacing transistor 216 in a non-conducting condition, and then allowinga current to be measured by placing transistor 216 in a conductingcondition.

[0050] The cycling of line conditions, in order to make the measurementsidentified previously, is controlled by a clock resident withinmicro-controller 201. After each condition has been set up, a twelve bitnumber is received from the digital to analogue converter 203 and thisnumber is retained within a respective register within micro-controller201. Thus, after completing a cycle of four measurements, four twelvebit values are stored within the micro-controller 201 for interrogationby the processing device 131. Furthermore, the rate of cycling may becontrolled in response to instructions received from the processingdevice 131.

[0051] Operations performed by micro-controller 201 are detailed in FIG.3. The micro-controller continually cycles between its fourconfiguration states and each time a new input is produced, representinga current or a voltage in one of the two configurations, new output datais calculated on an on-going basis. Thus, output registers are updatedsuch that the best data is made available if the micro-controller isinterrupted by the external processor 131.

[0052] The micro-controller 201 is fully interrupt driven in terms ofreceiving external interrupts for data interrogation along with internalinterrupts in order to initiate a configuration cycle. The externalinterrupt has a higher priority such that external processor 131 isprovided with information as soon as possible in response to making aninterrupt request.

[0053] Internally interrupts for the micro-controller 201 are generatedby its own internal timer and the procedure shown in FIG. 3 iseffectively held in a wait state until a next timer interrupt isreceived at step 301. The wait state allows voltage levels onconnections 107, 108, 111 and 112 to become stable and providessufficient time for valid data to be received from the analogue todigital converter 203.

[0054] At step 302, an output is received from analogue to digitalconverter 203 and at step 303 calculations are performed with respect tothe most current data received from the analogue to digital converter,so as to convert numerical values relating to voltages and currents intonumerical values representing properties of the mechanical interaction.Thus, after performing calculations at step 303, appropriate registersare updated at step 304 and it is these registers that are interrogatedin response to an interrupt received from processing system 131.

[0055] At step 305 next conditions for the output lines are set byappropriate logic levels being established for output pins CO to C6.After the next output condition has been selected, the processor entersa wait state at step 306, allowing the electrical characteristics tosettle, whereafter processing continues in response to the next timerinterrupt.

[0056] Thus, it should be appreciated that on each iteration of theprocedure shown in FIG. 3, one of the output conditions is selected atstep 305. Thus, it should be appreciated that the input data iseffectively delayed and does not represent a condition of the electricalcharacteristics at an instant. If in practice, the delay betweenmeasurements becomes too large, it becomes necessary to enhance thefrequency of operation of circuits within the control system shown inFIG. 2. Thus, the rate of conversion for converter 203 would need to beincreased and the circuitry would need to be redesigned for highfrequency operation. This in turn could create problems in terms of highfrequency interference resulting in enhanced shielding being requiredfor the facility as a whole.

[0057] When output condition number one is selected, an output voltageat 108 is determined. On the next cycle, identified as output conditionnumber two, the current flowing through connector 108 is determined. Onthe next iteration, under output configuration number three, the voltageappearing at connector 112 is determined and on the next cycle,identified as condition number four, the current flowing throughconnector 112 is determined. After each of these individualmeasurements, new data is generated in response to steps 303 and 304such that resulting output registers are being regularly updated on acontinual basis, such that the processing system 131 may effectivelyperform a continual monitoring operation in terms of changes made to themechanical interactions with the detector 101.

[0058] In a typical implementation, the four characteristicmeasurements, making up a complete cycle, will be repeated at afrequency of between twenty-five to fifty times per second. Insituations where such a repetition rate is not required, it may bepreferable to increase the duration of the wait states and therebysignificantly reduce overall power consumption.

[0059] Planes 102, 103 and 104 of the detector 101 are detailed in FIG.4. Planes 101 and 103 are of substantially similar construction and areconstructed from fabric having electrically conductive elements 402 inplane 102 along with similar electrical conductive elements 403 in plane103. Thus, it is possible for a voltage indicative of position to bedetermined when conductive elements 402 are placed in physical contactwith conductive elements 403.

[0060] The overall resistivity of planes 402 and 403 are controlled bythe inclusion of non-conducting elements 404 and 405. Thus, resistivityis controlled by controlling the relative quantities and/or densities ofconductive elements 402 with non-conductive elements 404. Resistivitymay also be controlled by selecting an appropriate fibre type, adjustingthe thickness of the fibre or adjusting the number of strands present ina yarn.

[0061] Plane 104 represents a non-conducting insulating spacerpositioned between the two conducting planes 102 and 103. Plane 104 isconstructed as a moulded or woven nylon sheet having an array ofsubstantially hexagonal holes 411, the size of holes 411 is chosen so asto control the ease with which it is possible to bring conductiveelements 402 into physical contact with conductive elements 403. Thus,if relatively small holes 411 are chosen, a greater force is required inorder to bring the conductive elements together. Similarly, if the sizeof the hole is increased, less force is required in order to achieve theconductive effect. Thus, the size of holes 411 would be chosen so as toprovide optimal operating conditions for a particular application.Operating conditions may also be adjusted by controlling the thicknessof layer 104, its surface flexibility and the contour of co-operatingplanes 102 and 103.

[0062] When a potential is applied across one of the conducting planes,the actual potential detected at a point on that plane will be relatedto the position at which the measurement is made. Thus, a direct voltagemeasurement from the co-operating plane gives a value from which apositional co-ordinate may be determined. By reversing the plurality ofthe planes and taking a measurement from the opposing plane, twocoordinates are obtained from which it is then possible to identify aprecise location over the planar surface.

[0063] In addition to measuring position on the planar surface, thepresent invention is directed at identifying additional electricalproperties in order to determine properties of the mechanicalinteraction. As previously described, the system is conFigured tomeasure currents in addition to measuring voltages.

[0064] When the two conducting planes are brought into mechanicalcontact, due to a mechanical interaction, the amount of current flowingas a result of this contact will vary in dependence upon the actualposition of the plane where the mechanical interaction takes place. Theposition of the mechanical interaction has also been determined withreference to voltages and it could be expected that these two quantitieswill vary in a substantially similar way, each representing the samephysical situation. Experience has shown that variations in measuredcurrent do not follow exactly the same characteristic as variations inmeasured voltage. As illustrated in FIG. 5, the amount of currentflowing due to a mechanical interaction will depend upon the position ofa mechanical interaction 501. However, in addition to this, the amountof current flow will also depend upon the size of the mechanicalinteraction. As the size of the mechanical interaction increases, thereis a greater area of contact and as such the overall resistance of themechanical interaction is reduced. However, it should be appreciatedthat variations in terms of current with respect to interaction size isa sophisticated relationship, given that, in addition to the resistivityof the contact area 501, the resistivity of the actual electricalconnections within the sheet must also be taken into account.

[0065] Thus, current is transmitted through a region 502 in order toprovide a current to the contact region 501. Some aspects of this effectwill be compensated with reference to position calculations and othervariations due to this effect may be compensated by a non-linearanalysis of the input data.

[0066] Contact area resistivity is illustrated generally at 510 andshows that the amount of current flowing between plane 102 and plane 103is considered as being related to the area of mechanical interaction,which is related to the area of contact externally and to the level ofexternally applied mechanical force.

[0067] The resulting non-linear relationship between the force areaproduct and the resulting current flow is illustrated generally at 520.At 521 there is an initial threshold point, identifying the point atwhich the gap starts to be closed, followed by an operational part ofthe curve 522 which may give useful indications of pressure up to point523, whereafter the relationship becomes very non-linear until position524 where the relationship effectively saturates.

[0068] Using a detector of the type illustrated in FIG. 1, it ispossible to measure current flow, which could also be considered ascontact resistance, in order to identify an additional mechanicalproperty of the interaction. As illustrated in FIG. 5, this othermechanical property is related to the area of contact between thesheets, determined by the amount of force applied to the sheets, and tothe total area over which the force is applied; or a combination ofthese two properties. Thus, data relating to force and area may giveuseful information relating to the interaction, separate from theposition at which the interaction takes place.

[0069] In some situations, such as when using a stylus or similarimplement, the area of applied force remains substantially constanttherefore a measurement of current will enable calculations to be madein terms of stylus pressure. Pressure sensitive styli are known but inknown configurations the pressure detection is determined within thestylus itself, leading to the stylus being mechanically connected tooperational equipment or requiring sophisticated wireless transmissionwithin the stylus itself. The present embodiment allows stylus pressureto be determined using any non-sophisticated stylus, given that thepressure detection is made by the co-operating fabric detector, arrangedto detect stylus position (with reference to voltage) in combinationwith stylus pressure, with reference to current.

[0070] An alternative construction for the conducting fabric planes isillustrated in FIG. 6. The detector includes a first conducting plane601 and a second conducting plane 602. In addition, woven into each ofthe conducting planes 601 and 602, there are a plurality ofnon-conducting nodes 605 arranged to mutually interfere and therebyseparate the two conducting planes. Between the nodes, the fabrics ofthe first and second planes may be brought into contact relativelyeasily such that the application of force, illustrated by arrow 611would tend to cause a finite number of regions interspersed betweennodes 605 to be brought into contact. Thus, for a particular region,contact either is taking place or is not taking place as illustrated bycurve 621.

[0071] With a number of such regions brought into contact, the overalllevel of current flow will tend to vary with the area of contact asillustrated by curve 631. Thus, using a construction of the type shownin FIG. 6, it is possible to obtain a more linear relationship, comparedto that shown in FIG. 5, in which the level of current flow gives a verygood indication of the area of coverage as distinct from the level offorce applied to the mechanical interaction.

[0072] Given a construction of the type shown in FIG. 6, an indicationof applied force or pressure may be obtained, in addition to an accuratedetermination of area, by providing an incremental switching operation.In the configuration shown in FIG. 7, there is provided a firstconducting plane 701 which interacts with a second conducting plane 702.Furthermore, conducting plane 702 interacts with a third conductingplane 704. Conducting plane 701 is separated from conducting plane 702by nonconducting portions 705. Similarly, plane 702 is separated fromplane 704 by non-conducting portions 706. More non-conducting portions706 are provided than similar non-conducting portions 705. Consequently,less force is required to produce electrical contact between planes 701and 702 than is required to produce an electrical contact between planes702 and 704. In this way, it is possible to provide an incrementalmeasurement of force, given that a low force will only cause contactbetween plane 701 and plane 702 whereas a larger force will also provideelectrical contact between plane 702 and 704.

[0073] An alternative configuration is shown in FIG. 8 in which it ispossible to obtain enhanced substantially continuous variations incurrent flow with respect to applied force. A first conducting plane 801interacts with a second conducting plane 802. The planes are woven insuch a way as to produce very uneven surfaces such that, under lightload, the level of interaction is relatively low. As load increases, asillustrated generally at 805, a greater level of surface contact shownat 806 is created thereby increasing the level of current flow in asubstantially continuous way. It should also be noted that thisconfiguration does not include an insulating layer as such and that alevel of current flow will always take place even under conditions ofzero load. Alternatively, a very thin insulating layer could beprovided, having a relatively low threshold, thereby resulting in a zerocurrent flow when no load is applied.

[0074] As shown by curve 811, the output current varies with respect tovariations in applied force for a constant load area. Similarly, asshown by curve 821, output current varies with respect to load area fora substantially constant applied force.

[0075] A composite configuration is shown in FIG. 9, in which a detector901, substantially similar to that shown in FIG. 6, is combined with adetector 902, substantially similar to that shown in FIG. 9. Detector901 provides an accurate measurement of applied area and it isrelatively unaffected by applied force. Detector 902, as shown in FIG.8, provides an output which varies with respect to area and force. Thus,by processing the output of these two detectors in combination, it ispossible to compensate the output from detector 902 in order to producevalues representing force, such that the two currents provideindications of both force and area.

[0076] The operation of the control circuit 121 is such as to apply afirst voltage across diagonals 107 and 108 with a similar voltage beingapplied across diagonals 111 and 112. The nature of the voltagedistribution is therefore asymmetric, but this does not result indifficulties provided that the area of contact between the two planes isrelatively symmetric. However, should an asymmetric area of contact bemade, as illustrated in FIG. 10, differences will occur in terms ofcurrent measurements when considering calculations made in the twodirections.

[0077] An asymmetric object 1001 is shown applied to the surface of adetector 1002. When a voltage is applied between contact 107 and 108,paths over which current may flow, illustrated generally at 1003 arerelatively large and the object is perceived as having a large area oris perceived as applying a large force. In the opposite dimension, whena voltage is applied between 111 and 112, the regions over which currentflow takes place illustrated generally at 1005, become relativelysmaller therefore the object would be perceived as having a relativelysmaller area or would be perceived as providing a-relatively smallerforce.

[0078] If the system is programmed to the effect that the object has aconstant area and applies a constant force, these differences in termsof current flow may be processed in order to give an indication as tothe orientation of the object. Thus, the system of the type illustratedin FIG. 10, is used in combination with the detector of the typeillustrated in FIG. 9 it is possible to make reference to the parametersof location in two-dimensions, force or pressure, the area ofapplication and orientation.

[0079] In the preferred embodiment, electrical characteristics ofvoltage and current are measured. Alternatively, it would be possible todetermine the resistance or the resistivity of the conducting sheets.Problems may be encountered when using alternating currents due toenergy being radiated from the conducting sheets. However, in somesituations it may be preferable to use alternating currents, in whichfurther electrical characteristics of the detector may be considered,such as capacitance, inductance and reactance etc.

[0080] The detector shown in FIG. 1, constructed from conducting planes102 and 103, operates satisfactorily if the plane of the detector ismaintained substantially flat. This does not create a problem in manyapplications where relatively flat operation is considered desirable.However, although constructed from fabric, thereby facilitating bendingand folding operations, the reliability of the detector in terms of itselectrical characteristics cannot be guaranteed if the detector planesare folded or distorted beyond modest operational conditions.

[0081] A detector is shown in FIG. 11, constructed from fabric havingelectrically conductive elements to define at least two electricallyconductive planes. The detector is conFigured to produce an electricaloutput in response to a mechanical interaction, as illustrated inFIG. 1. At least one of the planes includes first portions and secondportions in which the first portions have a higher resistance than saidsecond portions and the first higher resistance portions are moreflexible than the second portions. In this way, flexing occurs at theportions of high resistance, where contact between the planes has littleeffect, while the lower resistance portions, where contact does have astrong electrical effect, remain substantially rigid such that theflexing of the material does not occur over these portions of thedetector.

[0082] Portions 1101 have a relatively high resistance compared toportions 1102. Portions 1101 are not involved in terms of creating anelectrical reaction in response to a mechanical interaction. Theelectrical responses are provided by the more rigid weave of portions1102. The purpose of portions 1101 is detailed in FIG. 11 B. A curvaturehas been applied to the detector but the configuration is such thatnormal operation is still possible. The flexing has occurredpredominantly at portions 1101. However, portions 1102 have remainedstraight thereby ensuring that they remain displaced from each other,even when a curvature is present, such that the detector is stillavailable for detecting the presence of a mechanical interaction.

[0083] The rigidity of portions 1102 may be enhanced as shown in FIG.12A. A first plane 1201 has rigid portions 1202 and flexible portions1203. A second plane 1204 has relatively rigid portions 1205 andrelatively flexible portions 1206. The relatively flexible portions 1206physically contact against similar portions 1203 in the first plane1201. In order to ensure that there is no, or at least minimalelectrical interaction at these points of contacts, the electricalresistance of the flexible portions 1203 and 1206 is relatively high. Apartially insulating layer may be provided between the conductinglayers, as shown in FIG. 1. However, the flexible portions 1203 act asinsulating separators therefore in this embodiment the provision of aseparation layer is not essential. Furthermore, the rigidity of theinteracting sections, in terms of the rigid portions 1202 and 1205, hasits rigidity further enhanced by the presence of relatively solidintermediate plates 1208.

[0084] Flexing of the construction shown in FIG. 12A is substantiallysimilar to that provided by the embodiment shown in FIG. 11 B. Theflexing of the embodiment shown in FIG. 12A is detailed in FIG. 12B.Flexing occurs at the position of the relatively flexible portions 1203and 1206. The rigidity of portions 1202 and 1205 is enhanced by theprovision of more solid plates 1208. Thus, the embodiment shown in FIGS.12A and 12B may have more strenuous flexing forces applied thereto suchthat mechanical interaction detection is maintained even under severeoperating conditions.

[0085] The provision of the flexible portions effectively provide linesover the surface of the conducting planes where folding is permitted.Thus, complex curvatures may be obtained by a number of folds beingeffected at a plurality of these preferred foldable lines, therebyallowing complex shapes to be attained while maintaining the desiredelectrical characteristics.

[0086] An alternative embodiment is shown in FIG. 13 in which a firstcooperating plane has flexible high resistive portions 1301 and rigidconducting portions 1302. This plane co-operates with a second plane1303 of substantially homogenous construction. Thus, sufficient flexingand insulation is provided by the non-conducting flexible portions 1301of the lower co-operating plane 1304. The rigidity of conductingportions 1302 may be enhanced in a fashion substantially similar to thatprovided by FIG. 12A as illustrated in FIG. 14. The device includes anouter plane 1401 of substantially homogenous conducting construction.Below this, there is provided a second co-operating plane 1402 and thetwo planes may be separated by an insulating layer not shown in theexample. The second plane or layer includes flexible non-conductingportions 1403 and more rigid conducting portions 1404, substantiallysimilar to those shown in FIG. 13. In addition, rigid plates 1405 areprovided below each rigid portion 1404 thereby significantly enhancingthe rigidity of these portions. Thus, the construction in FIG. 14 iscapable of withstanding more aggressive working environments compared tothe lighter construction shown in FIG. 13. In the construction shown inFIGS. 13 and 14 the outer layers, 1303 and 1401 respectively, arefabricated in a substantially elastic fashion, thereby providing for astretching or extension of this layer during flexing operations.

[0087] The detector shown in FIG. 1 is capable of accurately detectingthe position of a mechanical interaction and as previously described, itis also possible to determine other characteristics of the mechanicalinteraction by modifying other electrical properties. A problem with thedetector shown in FIG. 1 is that it experiences difficulties if morethan one unconnected mechanical interaction takes place. If a firstmechanical interaction were to take place and, simultaneously, a secondmechanical interaction were to take place, displaced from the first, itwould not be possible, using the configuration shown in FIG. 1, toidentify the presence of two mechanical interactions. A condition wouldbe detected to the effect that a mechanical interaction is taking placebut the system would tend to perceive this as a single mechanicalinteraction having characteristics substantially similar to the averageof the characteristics of the two independent interactions.

[0088] An alternative embodiment for overcoming problems of this type isshown in FIG. 15. In FIG. 15, a plurality of detectors 1501, 1502, 1503,1504, 1505, 1506 and 1507 have been connected together and each of theseindividual detectors has its own unique connectors 1511, 1512, 1513 and1514. In this way, each of the individual detectors may be connected toits own respective control circuit, such as circuit 121 shown in FIG. 1or, in an alternative embodiment, a single control circuit of the typeshown in FIG. 1 may be shared, using a switching arrangement, betweenall seven of the individual combined detectors. In this way, eachindividual detector, such as detector 1501, provides the same level ofaccuracy as the detector shown in FIG. 1. However, if two or moremechanical interactions take place on different detector sections, it ispossible to detect this condition and provide appropriate outputresponses. However, it is only possible to detect a plurality ofmechanical interactions if these interactions take place on differentsections and it is not possible for the embodiment shown in FIG. 15 todetect a plurality of interactions if these interactions take place onthe same section.

[0089] In the arrangement shown in FIG. 15, the detectors have beenarranged in strips such that there is enhanced definition in thedirection of arrow 1521 but the definition in the direction of arrow1522 has not changed.

[0090] In the detector shown in FIG. 1, position detection is madepossible using four electrical connection cables, a first two connectedto opposing diagonal corners of the upper sheet and a further twoconnected to the alternative opposing diagonal corners of the lowersheet. An alternative configuration is shown in FIG. 16 in whichelectrical connectors 1601, 1602, 1603 and 1604 are connected torespective corners 1611, 1612, 1613 and 1614 of a lower plane conductingsheet 1621. An upper plane conducting sheet 1622 is connected to asingle detecting cable 1631 connected at a position 1632 towards an edgeof upper conducting sheet 1622. A disadvantage of the configurationshown in FIG. 16 is that five separate electrical connections arerequired whereas only four electrical connections are required in theconfiguration shown in FIG. 1. However, in some circumstances, theconfiguration shown in FIG. 16 does have advantages over that shown inFIG. 1.

[0091] The configuration shown in FIG. 16 may be used to effectivelymultiplex the operation of a detector so as to facilitate the detectionof a plurality of mechanical interactions to a greater extent than -theconfiguration shown in FIG. 15. In particular, it facilitates detectingmultiple mechanical interactions in both dimensions of the planardetector.

[0092] As shown in FIG. 17, a lower planar sheet 1701 has connections1702, 1703, 1704 and 1705 at each of its corners. Thus, sheet 1701operates in a way which is substantially similar to the operation ofsheet 1621 and all output voltages are generated within this sheet,either across diagonal 1702 to 1704 or across diagonal 1703 to 1705,thereby giving a two-dimensional co-ordinate within the area of thesheet.

[0093] An upper planar sheet 1721 is divided into a plurality ofportions. In the example shown, eight portions 1731 to 1738 areprovided. Thus, the mechanical action results in conducting planes of atleast one of said regions being brought into electrical interaction withthe lower plane 1701. Furthermore, if a mechanical interaction occurs atregion 1731 and a second mechanical interaction occurs at region 1735(for example) both of these mechanical interactions may be determinedindependently and an output to this effect may be generated by aprocessing system, such as system 131.

[0094] In order to achieve the space division multiplexing provided byregions 1731 to 1738, time division multiplexing of the electricalsignals is performed in which, during each individual time slot, oneindividual region 1731 to 1738 is considered. This is achieved by eachindividual region 1731 to 1738 having its own respective electricalconnector 1741 to 1748. These connectors are preferably incorporated into the structure of the sheet.

[0095] Control circuitry for the configuration shown in FIG. 17 requiresmodification compared to that shown in FIG. 2. In particular, each ofthe eight output control lines 1741 is supplied to its own respectivebuffering amplifier, similar to amplifiers 2223 and 2223 and the outputfrom each of these eight amplifiers is applied to appropriate switchingdevices, allowing one of eight inputs to be selected using a pluralityof switches substantially similar to switch 2221.

[0096] A complete scanning cycle consists of applying a voltage betweeninput terminals 1702 and 1704. An output is then considered from eachindividual output terminals 1741 to 1748. The voltages are then reversedsuch that a voltage is applied between output terminals 1705 and 1703.Each of the individual input terminals is then considered again so as toprovide two-dimensional co-ordinates within each of the individualregions 1731 to 1748. As described with respect to FIG. 2, both voltagesand currents may be considered in order to provide additionalmechanically related information, such as pressure related informationetc.

[0097] In the detector configuration shown in FIG. 1 and in alternativedetector configurations, such as that shown in FIG. 15 and that shown inFIG. 16, it is necessary to provide electrical connection betweenprocessing equipment and the detector fabric itself. Techniques for theaddition of electrical connectors to current conveying fabrics areknown. However, in the known techniques, continual wear and usage .ofthe detector assembly often results in electrical connectors becomingdisconnected from the material fabric, resulting in total systemfailure. It is therefore highly desirable to provide a system in whichthe electrical connector is held very securely to the material fabricitself so as to provide a robust system which does not becomedisconnected through continual use.

[0098] An improved approach to providing electrical connection to theelectric current carrying conductors within the fabric is illustrated inFIG. 18. Further modification is shown in FIG. 19. In both of thesesystems, the fabric is constructed from electrically conducting fibresand from electrically insulating fibres by a mechanical process, such asweaving or knitting. An improved electrical connection is achieved byconnecting electrical connection devices to the electrically conductingfibres of the fabric forming the detector during the mechanical fabricgenerating process. Thus, in the embodiments shown in FIG. 18 and FIG.19, there is no requirement for adding connectors after a fabric hasbeen created. The provision of a connector to the electric currentcarrying fibres is achieved during the actual mechanical process itself.Thus, for example, if the fibres are being produced by a knittingoperation, part of this knitting operation involves procedures by whichthe electrical current carrying connector is actually included as partof the overall knit.

[0099] Fibres 1801 making up the weave are illustrated in FIG. 18. Aweaving procedure may be considered as generating woven fabric bytraversing in the direction of arrow 1802. At pre-programmed positions,or at manually selected positions, modifications are made to the weavingprocess to the effect that a connector 1803 is to be introduced.

[0100] In the example shown in FIG. 18, connector 1803 is an insulationdisplacement connector (IDC) allowing an insulated wire to be connectedin such a way that it is not necessary to remove the insulation from thewire, given that the insulation is effectively cut as the wire,illustrated by reference 1804 is inserted into the connector in thedirection of arrow 1805.

[0101] The weaving procedure is modified such that connector 1803 isincluded as part of the weave and is thereby held relatively firmlyafter the weaving procedure has been completed. In order to provide afurther enhanced mechanical connection between electrical connector 1803and the remaining woven fabric, additional layers of electricallyconducting epoxy resin 1805 and 1806 are applied, such that, inoperation, physical force applied to connector 1803 will not, undernormal circumstances, be displaced from the woven material of the deviceand will maintain electrical integrity.

[0102] A similar configuration is shown in FIG. 19 in which a rivetfastener 1901 is applied during a weaving or knitting process, therebysubstantially embedding the rivet fastener within the overall weave orknit. After the rivet fastener has been secured by the woven fabric1902, electrically conducting epoxy resin 1903 is applied to provideenhanced mechanical and electrical stability.

[0103] In the configuration shown in FIG. 1 and in the configurationshown in FIG. 16, an electrical field is established over thetransmitting plane. Given a plane of infinite size, the electrical fieldwould have a regular geometric distribution and the position of amechanical interaction could be determined from two voltage measurementsin a substantially straightforward way. However, in the configurationshown in FIG. 1 and FIG. 16, edges are present and these edges introducesevere distortions to the nature of the electric field from whichmeasurements are being taken. In the control circuit 121 and within thedata processing system 131 it is possible to provide a level ofcompensation, possibly in response to empirical measurements but such anapproach has disadvantages, one of which being a loss of resolution.

[0104] Systems are shown in FIGS. 20 and 21 in which a detector isconstructed from fabric having electrically conductive elements todefine at least two electrically conducting planes. The detector isconFigured to produce an electrical output in response to a mechanicalinteraction. The relationship between mechanical interaction andelectrical output is enhanced by introducing a conductivitynon-uniformity which is included in at least one of the planes so as tomodify an electrical response to the mechanical interaction.

[0105] In FIG. 20, an electrical connector 2001 is connected to a planeat a first corner and a second connector 2002 is connected to thediagonally opposing corner. A configuration of this type could be usedfor a detector of the type shown in FIG. 1, in which the electricalfield effectively traverses across the diagonal corners, resulting indistortions at the edges. In the embodiment shown in FIG. 20, aconducting thread 2003 with relatively low resistivity is includedacross edge 2004, electrically connected to connector 2001. Similarly, asecond conducting thread 2005, with relatively low resistivity, extendsfrom electrical connection 2002 along edge 2006. In this way, the wholeof edge 2004 becomes conducting and the whole of edge 2006 becomesconducting. The resulting electric field is then substantially linearthroughout the length of the detector thereby substantially eliminatingnon-linear edge effects.

[0106] In its co-operating plane 2010 a low resistance conducting thread2011 is included along edge 2012 and a similar conducting thread isprovided along the opposing edge. In this way, the electric fieldtraverses in a direction which is orthogonal to the electric fieldprovided in the upper sheet, thereby allowing co-ordinates defined inmutually orthogonal coordinate space.

[0107] A conducting material is shown in FIG. 21 in which areas 2101,close to all four edges, have had their conductivity modified, such thatthe overall conductivity of the sheet is non-uniform. This modificationto conductivity may be achieved in several ways, including the additionof a conducting thread of the type illustrated in FIG. 20.Alternatively, the modification to conductivity, to provide conductivitynon-uniformity, may be achieved by a printing operation in whichelectrically conducting inks, possibly including silicon, are printed atregion 2101. Alternatively, the density of conducting fibres in thewoven material itself may be modified towards the edges of the detector,again resulting in a conductivity non-uniformity. Furthermore, it shouldbe appreciated that modifications of this type may be achieved usingcombinations of the above identified effects in order to tailor therequired level of non-uniformity for a particular application.

[0108] In the configuration shown in FIG. 1, a cycle is performed inwhich upper plane 102 effectively transmits allowing signals to bereceived by lower plane 103. A co-ordinate position is identified byreversing the operation of these planes, such that certain parts of thecycle include situations in which the lower plane 103 is effectivelytransmitting and the upper plane 102 is effectively transmitting. In aconfiguration of this type, it is preferable for the material types tobe similar so as to provide substantially similar operations when plane102 is transmitting or when plane 103 is transmitting. This is aparticularly important constraint when the system is being used tomeasure current flow, given that different resistivities could beachieved in the different directions of current flow.

[0109] In the configuration shown in FIG. 16, transmission always occursfrom plane 1621, although in different orientations, and detectionalways occurs from plane 1622. With a configuration of this type,current always flows in the same direction therefore it is not essentialfor planes 1621 and 1622 to have equivalent mechanical constructions.

[0110] In the configuration shown in FIG. 16, a detector is constructedfrom fabric having electrically conductive elements to define at leasttwo electrically conductive planes and configured to produce anelectrical output in response to a mechanical interaction. A secondelectrically conductive plane, such as plane 1622 of the detector, hasat least one electrical characteristic that differs significantly invalue from the value of said characteristic of the first plane 1621.

[0111] In the detector shown in FIG. 16, the upper receiving plane 1622has a significantly lower resistance than the lower transmitting plane1621. In this way, as the area of mechanical interaction increases, theamount of current flow increases significantly, thereby improving thedefinition of the system with respect to changes in the size of themechanical interaction, and allowing for less intensive calculationswhen determining force etc.

1. A position detector constructed from fabric having electricallyconductive elements, comprising at least two electrically conductingplanes, wherein an electric potential is applied across at least one ofsaid planes to determine the position of a mechanical interaction; and asecond electrical property is determined to identify additionalproperties of said mechanical interactions.
 2. A position detectoraccording to claim 1 , configured to measure current or resistance assaid second electrical property.
 3. A detector according to claim 1 ,configured to determine applied force, applied pressure, area of contactor orientation of an object as the additional property of saidmechanical interactions.
 4. A detector according to claim 1 , includingprocessing means for modifying a second electrical characteristic withrespect to a measurement made for said first electrical characteristic.5. A detector according to claim 1 , wherein said fabric is constructedto facilitate measurement of area or said fabric is constructed tofacilitate the measurement of pressure or force.
 6. A detector accordingto claim 1 , wherein composite layers of fabric are provided to enhancemeasurement of a property or to facilitate the measurement of multipleproperties.
 7. A detector according to claim 6 , wherein multipleproperties are measured and a measurement of a first property is used tocompensate measurement of a second property.
 8. A detector according toclaim 1 , wherein a stylus is applied to the detector such that a firstelectrical property of a mechanical interaction determines the positionof the interaction and a second electrical property determines the forceor pressure applied to the stylus.
 9. A detector according to claim 1 ,wherein the detector interacts mechanically with parts of a human body;a first electrical property determines the position of a mechanicalinteraction and a second electrical property determines the area ofcoverage.
 10. A detector according to claim 1 , wherein electronicswitching means are provided to change electrical configurations to thedetector and analogue to digital conversion means are configured toconvert analogue signals to digital representations of said signals forsubsequent mechanical property calculations.
 11. A method of detection,performed with respect to a detector constructed from fabric and havingelectrically conducting elements configured to provide at least twoelectrically conducting planes, comprising the steps of applying apotential across at least one of said planes to determine the positionof a mechanical interaction; and measuring a second electrical propertyto identify additional properties of said mechanical interactions.
 12. Adetector constructed from fabric having electrically conductive elementsto define at least two electrically conductive planes and configured toproduce an electrical output in response to a mechanical interaction,wherein at least one of said planes includes first portions and secondportions, said first portions have a higher resistance than said secondportions and said first higher resistance portions are more flexiblethan said second portions.
 13. A detector according to claim 12 ,wherein said high resistance portions are configured as flexibleportions to facilitate rotational movement about similar portions in aco-operating conductive plane.
 14. A detector according to claim 13 ,wherein said conductive elements are separated from similar elements ofa co-operating plane by being supported by said flexible portions.
 15. Adetector according to claim 12 , wherein said second portions arefurther supported by solid portions.
 16. A detector according to claim15 , wherein said solid portions are constructed from rubber, silicon orplastics.
 17. A detector according to claim 12 , wherein only one ofsaid planes includes first high resistive flexible portions with secondportions and a co-operating plane is substantially homogeneous.
 18. Adetector according to claim 17 , wherein said homogeneous planefacilitates elastic expansion.
 19. A method of constructing a detectorfrom fabric, wherein electrically conductive elements are configured todefine at least two electrically conductive planes so as to produce anelectrical output in response to a mechanical interaction; wherein atleast one of said planes includes first portions and second portions;said first portions have a higher resistance than said second portions;and said first higher resistance portions are more flexible than saidsecond portions.
 20. A detector constructed from fabric havingelectrically conductive elements and configured to produce electricaloutputs in response to mechanical interactions, wherein said detector isdivided into a plurality of regions; each of said regions includes afirst conducting plane and a second conducting plane; a mechanicalinteraction results in conducting planes of at least one of said regionsbeing brought closer together; and a potential is applied across atleast one of said planes to determine the position of said mechanicalinteraction.
 21. A detector according to claim 20 , wherein at least oneof said conducting planes is unique to a region and the co-operatingconducting plane is shared with a plurality of regions.
 22. A detectoraccording to claim 21 , wherein a single co-operating conducting planeis shared with all of said regions.
 23. A detector according to claim 20, wherein signals are derived independently from a plurality of regionsby a time division multiplexing operation.
 24. A detector according toclaims 20, wherein a second electrical property is determined toidentify additional properties of said mechanical interactions.
 25. Amethod of constructing a detector from fabric having electricallyconductive elements and configured to produce electrical outputs inresponse to mechanical interactions, said detector being configured suchthat a potential is applied across at least one of said planes todetermine the position of the mechanical interaction, said methodcomprising the steps of dividing the detector into a plurality ofregions; providing a first conductive plane and a second conductiveplane for each of said regions; bringing together conductive planes ofat least one of said regions in a response to a mechanical interaction.26. A fabric constructed from electrically conducting fibres and fromelectrically insulating fibres by a mechanical process, whereinelectrical connection means are connected to electrically conductingfibres of said fabric during said mechanical process.
 27. A fabricaccording to claim 26 , wherein said mechanical process is a knittingoperation or a weaving operation.
 28. A fabric according to claim 26 ,wherein said connector is an insulation displacement connector.
 29. Afabric according to claim 26 , wherein said connectors are enclosedwithin conducting epoxy resin, ink or silicone.
 30. A method ofconstructing a fabric from electrically conducting fibres and fromelectrically insulating fibres by a mechanical process, comprising thesteps of providing a supply of electrical connection devices forelectrical connection to electrically conducting fibres of said fabric;modifying the mechanical process at selected positions so as toincorporate the electrically conducting device as part of the fabric;and applying sealing means to said electrically conducting device so asto secure said devices to the machined fabric.
 31. A detectorconstructed from fabric having electrically conductive elements todefine at least two electrically conducting planes and configured toproduce an electrical output in response to a mechanical interaction,wherein a potential is applied across at least one of said planes todetermine the position of a mechanical interaction and said secondelectrical property is determined to identify additional properties ofsaid mechanical interactions; and a conductivity non-uniformity isincluded in at least one of said planes so as to modify an electricalresponse to a mechanical interaction.
 32. A detector according to claim31 , wherein said conductivity non-uniformity includes a co-operatingpair of conducting strips configured to generate a substantially linearelectric field within said conducting planes.
 33. A detector accordingto claim 32 , wherein said strips are applied to each of said conductingplanes at mutually orthogonal locations.
 34. A detector according toclaim 31 , wherein all edges of a conducting plane are modified.
 35. Adetector according to claim 31 , wherein said conductivitynon-uniformity is defined by adjusting the density of conductingthreads.
 36. A detector according to claim 31 , wherein saidconductivity non-uniformity is created by printing conductive materialsonto the detector.
 37. A method of constructing a detector from fabricconfigured to produce an electrical output in response to mechanicalinteractions said detector being configured such that a potential isapplied across at least one of said planes to determine the position ofa mechanical interaction and a second electrical property is determinedto identify additional properties of said mechanical interactions, saidmethod comprising the steps of defining at least two electricallyconducting planes from electrically conductive elements and introducinga conductivity non-uniformity in at least one of said planes so as tomodify an electrical response to a mechanical interaction.
 38. Adetector constructed from fabric having electrically conductive elementsto define at least two electrically conductive planes and configured toproduce an electrical output in response to a mechanical interaction,wherein a second electrically conductive plane of said detector has atleast one electrical characteristic that differs significantly in valuefrom the value of said characteristic of the first plane.
 39. A detectoraccording to claim 38 , wherein one of said planes is used as a detectorand voltages are applied sequentially in different directions to theother co-operating plane.
 40. A detector according to claim 38 , whereinsaid electrical characteristic is electrical resistance.
 41. A positiondetector according to claim 38 , wherein a second electrical property isdetermined to identify additional properties of said mechanicalinteractions.
 42. A detector according to claim 38 , configured tomeasure current or resistance at said second electrical property andconfigured to determine applied force, applied pressure, area of contactor orientation of an object as the additional property of saidmechanical interactions.
 43. A method of constructing a detector,comprising the steps of constructing electrically conductive elementsfrom fabric to define at least two electrically conducting planesconfigured to produce electrical output in response to a mechanicalinteraction; and configuring a second electrically conductive plane ofsaid detector with at least one electrical characteristic that differssignificantly in value from the value of said characteristic of saidfirst plane.